Field of the Invention
The invention relates to an antenna to be applied with a high frequency current for generating an inductively coupled plasma in a vacuum chamber, and a plasma processing device that generates an induced electric field in the vacuum chamber by applying a high frequency current to the antenna disposed in the vacuum chamber to generate an inductively coupled plasma and process a substrate with the plasma. In this application, ions refer to positive ions. The processing applied on the substrate, for example, includes forming a film by a plasma CVD (chemical vapor deposition) process, etching, ashing, sputtering, or the like.
Description of Related Art
The conventional technology has proposed an antenna for generating an inductively coupled plasma (abbreviated as ICP) in a vacuum chamber by an induced electric field that is generated by applying a high frequency current to the antenna, and a plasma processing device including the antenna.
In this type of plasma processing device, the impedance of the antenna increases as the antenna is lengthened to cope with a large-size substrate. Consequently, a large potential difference occurs between two ends of the antenna. Under the influence of the large potential difference, plasma uniformity, such as the plasma density distribution, potential distribution, and electron temperature distribution, deteriorates and results in poor uniformity of the substrate processing. Moreover, as the impedance of the antenna increases, it also becomes difficult for the high frequency current to flow to the antenna.
Several plasma processing devices having the configuration of the antenna and the condenser being connected in series have been proposed in order to solve these issues.
For example, Patent Literature 1 (Japanese Patent Publication No. 2002-510841) proposes a plasma processing device that has an external antenna (i.e. an antenna disposed outside the vacuum chamber; the same hereinafter). In this device, a plurality of linear conductors that constitute a loop-shaped antenna are arranged side by side in the upper portion (external) of a dielectric window which forms a part of the vacuum chamber, and the condenser is connected in series to a return conductor of the loop-shaped antenna, which is far away from the dielectric window.
Patent Literature 2 (Japanese Patent Publication No. H11-317299) discloses a plasma processing device that has an internal antenna (i.e. an antenna disposed in the vacuum chamber; the same hereinafter). In this device, a plurality of linear antennas passing through an antenna conductor in an insulating pipe are arranged side by side in the vacuum chamber and the antennas are connected in series by the condenser disposed outside the vacuum chamber.
Patent Literature 3 (Japanese Patent Publication No. 2012-133899) discloses a plasma processing device having an internal antenna. In this device, a planar antenna (planar conductor) has one main surface located in the vacuum chamber, and one or more grooves that extend in a direction intersecting the flowing direction of the high frequency current are formed on the main surface to divide the main surface into a plurality of regions. In each groove, a condenser is disposed, such that each region of the planar antenna and each condenser are electrically connected in series.